Inter-distance adjusting conveyor, conveying method, and irradiation device

ABSTRACT

A conveyor arrangement comprises conveying elements defining a closed loop path having portions with substantially differing slopes. Driving elements are arranged to drive the conveying elements around the closed loop path. A plurality of arm elements are pivotably connected to the conveying elements. Carrier elements are pivotably connectable to the arm elements. Guiding elements are arranged in the vicinity of the closed loop path. A follower member arrangement of the arm elements comprises a first engaging element ( 18 -A) and a second engaging element. The first engaging element is forced in contact with a first section of the guiding element during a first part of the travel along the closed loop path. Similarly, the second engaging element is forced in contact with a second section of the guiding elements during a second part of the travel along the closed loop path.

TECHNICAL FIELD

[0001] The present invention relates generally to conveyor systems andin particular to closed loop conveyor systems providing adjustableinter-distances between the transported items.

BACKGROUND

[0002] In many industrial processes, items have to be transported fromone place to another, or through a processing area, where the items aretreated in different ways. A common example is an assembly line, whereitems are passing from one station to the other and where e.g. new partsare mounted at each station. Other examples are treatment of items, suchas painting, annealing or irradiation, where the items pass through aprocessing area in which the treatment is performed. In all such cases,different kinds of conveyor systems are necessary.

[0003] A common type of conveyor system comprises a conveying means,e.g. a linked chain or a wire, which is formed as a closed loop. Theconveying means is typically driven by a motor using a wheel or gearwheel. Supporting members are attached pivotably at the conveying means,typically at regular distances. The supporting members are connectableto carriers, in which the items are transported, or to the itemsthemselves. The position of the supporting member is typically definedby the gravitational forces, in which cases the carriers typicallyalways are directed downwards or by guiding means. When transportingitems along a path including alternating horizontal and verticalsections, the dimensions of the transported items will play an importantrole. When making a 90-degree turn, from horizontal to vertical, oneitem may collide with the following, if not enough space is providedbetween them. One may from simple model reasoning understand that thespace between the items has to be at least equal to the item height, inorder to avoid collision. Conveyor arrangements of this type thustypically transport items separated with a certain distance.

[0004] In many applications, the interspace between the items isdisadvantageous. If the items are going through a treatment, theefficiency of the treatment is reduced by the space between the items.Also, e.g. at loading or unloading, it is normally advantageous if thereis no space between the items.

[0005] In the patent application GB 2 067 968, a conveyor arrangement isdisclosed, which shows a planar closed-loop conveyor. A positioningarrangement is pivotably attached to a linked chain, and a carrier meansis rotatably attached to the positioning arrangement. A follower memberprovided with a rotatable roller is attached at an arm at thepositioning arrangement. The pivotable attachment point follows thechain path, while the follower member follows a guide means. Therelative distance between the guide and the chain path decides the angleof the positioning arrangement and thus the relative position of thecarrier means. A second positioning arrangement is rigidly attached tothe carrier means. Two follower members are arranged at this secondpositioning arrangement, following two further guides. The relativedistance between the two further guides determines the angle of thesecond positioning arrangement. By suitable choice of guidingstructures, the carrier means can be positioned in almost any arbitrarydirection. This positioning may indeed be very flexible, but the use ofa multitude of guides and follower members are far too complex in mostcases and occupies too much space for many treatment applications.

[0006] In the patent application DE 195 10 649, a conveyor device isdisclosed, which provides for an adaptive distance between thetransported items. A conveying linked chain supports carrier means alonga path. At a chain joint between the attachment points of the carriermeans, an arm member is attached. The arm member is provided with afollower member, which is guided along a rail arrangement, forcing thechain to bend. The bent chain makes the carrier means to be positionedcloser to each other, i.e. gives rise to the adjustable distances. Thisconveyor has the disadvantage that the conveying means, i.e. the chain,is bent at the same time as it is supposed to drive the carrier meansforwards. The forces and friction involved in such arrangements aregenerally high, and the total arrangement is space requiring.

[0007] In many applications, the available space around the conveyorpath is limited. A general disadvantage with conveyor arrangements foradjustable item distances is that they demand quite complex and spacerequiring guiding means. Furthermore, angle-determining arm structuresaccording to prior art have limited angle strokes, within which they arestable and well determined.

SUMMARY

[0008] A general object of the present invention is to provide animproved conveyor arrangement for limited conveyor spaces. A furtherobject is to provide a conveyor arrangement having a simple and reliabledesign. It is also an object of the present invention to provide aconveyor arrangement, which is capable of changing the distance betweenthe transported items during certain parts of the conveyor path. Anotherobject of the present invention is to provide a conveyor arrangementhaving mechanically well defined paths.

[0009] The above objects are achieved by conveyor arrangements andconveying methods according to the enclosed claims. In general words, aconveyor arrangement comprises conveying means defining a closed looppath. The path has portions with substantially differing slopes. Drivingmeans are arranged to drive the conveying means around the closed looppath. A plurality of arm means are pivotably connected to the conveyingmeans around a substantially horizontal axis and follows the conveyingmeans along the closed loop path. Carrier means are pivotablyconnectable to the arm means.

[0010] Guiding means are arranged in the vicinity of the closed looppath. A follower member arrangement of the arm means comprises a firstengaging means and a second engaging means. The first engaging means isforced in contact with a first section of the guiding means during afirst part of the travel along the closed loop path. Similarly, thesecond engaging means is forced in contact with a second section of theguiding means during a second part of the travel along the closed looppath.

[0011] In preferred embodiments of the present invention, the first andsecond parts of the travel have no common parts. At the most one of theengaging means is therefore forced in contact with the guiding means ata time. The first and second engaging means are preferably provided atopposite sides of a connection line between the attachment axis of thearm means and the centre of the connection of the carrier means. Theengaging means are preferably protrusions provided with rollers. Thesize and distance from the conveying means may be different for the twoengaging means.

[0012] In a preferred embodiment the arm means comprises at least twocarrier supporting members, and the carrier means have correspondingcatching means for releasable engagement with each one of the carriersupporting members. When the engaging means are active, only one carriersupporting member is in engagement with the catching means.

[0013] With the arrangement according to the present invention theposition and speed of the carrier means can be adjusted within certainranges. The front engaging means, as defined by the arm traveldirection, is guidable in front of the connection point between the armmember and the conveying means. Similarly, the rear engaging means isguidable in front of the connection point. This influences the positionand hence the inter-distance between consecutive carrier means. Byguiding any of the engaging means forwards in relation to the connectionpoint, the carrier means is given a speed, which exceeds the speed ofthe conveying means. By guiding any of the engaging means backwards inrelation to the connection point, the carrier means is instead given aspeed which is less than the speed of the conveying means.

[0014] According to another aspect of the invention, an irradiationequipment is presented, which uses the advantages of a conveying systemaccording to the above description.

[0015] The advantage with the present invention is that a simple armmeans arrangement allows for a mechanically safe tilting within a largeangle range. This reduces the need for long arm lengths, whereby sucharrangements can be used also in small spaces. By proper selection ofthe guiding structure form and the path of the closed loop, almost anymotion of the carrier means may be obtainable.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The invention, together with further objects and advantagesthereof, may best be understood by making reference to the followingdescription taken together with the accompanying drawings, in which:

[0017]FIGS. 1a and 1 b are simple sketches of conveyor arrangements witharm means according to prior art;

[0018]FIG. 2 is a sketch for explaining the need for inter-distancesbetween conveyed objects;

[0019]FIG. 3 is a principle sketch of the function of an arm memberaccording to prior art;

[0020]FIGS. 4a-d are principle sketches of different aspects of thefunction of an arm member according to the present invention;

[0021]FIG. 5 is an illustration, partly exploded and with partsexcluded, of an irradiation equipment according to the presentinvention;

[0022]FIG. 6 shows an arm member used in the equipment shown in FIG. 5;

[0023]FIG. 7a shown a carrier box used in the equipment shown in FIG. 5;

[0024]FIG. 7b illustrates the engagement of arm members according toFIG. 6 and a carrier box according to FIG. 7a;

[0025]FIG. 8 illustrates guiding surfaces and chain guiding blocks usedin the equipment shown in FIG. 5;

[0026]FIG. 9 illustrates the motion of an arm member along the devicesin FIG. 8; and

[0027]FIG. 10 is a flow diagram illustrating the basic steps of aconveying method according to the present invention.

DETAILED DESCRIPTION

[0028] Closed-loop conveyor arrangements have a conveyor path, alongwhich the conveyor means is driven, typically in a constant speed. Itemsto be transported are in different ways attached to the conveyor means.In many applications it is desirable to control the angle of the itemreferred to the conveyor path and/or the distance between twoconsecutive items in a well reproducible manner at certain positions orpath portions.

[0029] One often used basic principle of such control is to connect theitems or carriers for items to the conveyor means by means of some typeof positioning arrangement, e.g. an arm arrangement. By separating thecarrier or item from the actual conveyor path by a certain distance,there is a possibility to modify angles of the carrier/item and/ordistances between them. The positioning arrangements are typicallypivotably attached to the conveyor means. An example of such a prior artarrangement is illustrated in numerals in order to increase thereadability of the figure. Here, a chain 10 is provided with pivotableaxes 13, to which one end of arms 14 are attached. The arms 14 are inthe opposite end rigidly attached to a carrier 16. The arm 14 is in itsmiddle part provided with a follower member 18. This follower member 18is guided by a guiding slot 20, which extends substantially parallel tothe path of chain 10. The chain 10 is moved in the direction of thearrow 12. By reducing the distance between the chain 10 path and theguiding slot 20, which is the case in the section 22, the arm 14, andthereby the carrier 16 is forced somewhat backwards, with reference tothe direction of motion 12 and the position of the attachment point,i.e. the axis 13. The average distance between to consecutive carriers16 within the section 22 is reduced as compared with the distancebetween consecutive axes 13. In section 24, the distance between theguiding slot 20 and the chain 10 is increased again, and the carriers 16are turned back to their original angular positions. The averagedistance between consecutive carriers 16 within this section 24 isclearly larger than in section 22. In this manner, the inter-distancebetween transported items has been adjusted in prior art.

[0030] In FIG. 1a, one notices that the carrier 16 is turned when theinter-distance is changed. If this behaviour is of disadvantage, one hasto provide for some additional positioning arrangement. In GB 2 067 968,this is achieved by the additional follower means on the secondpositioning arrangement. If the conveyor path is arranged substantiallyin the vertical direction, i.e. having vertical and horizontal portions,gravitational forces may be utilised for controlling the carrier angle.Such a system is illustrated in FIG. 1b. The attachment of the arms 14to the carriers is here pivotable, and the gravitation keeps the carriersubstantially horizontal during the entire travel. All other parts areidentical to the arrangement in FIG. 1a and are not described again. Thechanging inter-distances between consecutive carriers are easilydistinguished also here.

[0031] In the following section, the reason for having iteminter-distances is explained more in detail. In FIG. 2, a part of aconveyor arrangement in the vertical plane is illustrated. A chain 10 isarranged to follow a path by means of two gear wheels 11 along thedirection of the arrow 12. Arms 14 are pivotably arranged at the chain10 and also pivotably attached to carriers 16. The carriers 16 are thuspositioned in their vertical direction by means of gravitational forces.The carriers 16 have a height h, a length in the motion direction of d,and the inter-distance between the items in the horizontal portions ofthe path is Δ_(h). The inter-distance in the vertical portions isdenoted by Δ_(v). When an arm travelling along the horizontal portionreaches a gear wheel 11, the transportation direction changes. Insteadof a horizontal motion, a vertical motion is given. Due to the finitesize of the carriers 16, an item has to be lifted up a distancecorresponding to its own height before a following carrier reaches theback edge of the carrier in front. Since the vertical and horizontalspeeds are equal, determined by the speed of the chain 10, the minimuminter-distance Δ_(h) is equal to the height h of the carrier. Similarly,Δ_(h) has to be at least equal to the carrier length d.

[0032] The simplest form of arm arrangement with a follower member ispresented in FIG. 3. Such an arrangement is available according to priorart. A chain 10 is driven in the direction of the arrow 12. The arm 14is pivotably attached both to the chain 10, by an axis 13, and to thecarrier 16, and the gravitational force maintains the direction of thecarrier 16. During the normal transport, when no inter-distanceadjustment is required, the carrier 16 is simply hanging down from thechain 10 in the arm 14. A follower member 18 may, however, be broughtinto contact with a guiding structure 20. The follower member 18 isthereby prohibited to continue in the same speed as the axis 13 betweenthe chain 10 and the arm 14, and it is forced backwards relative to theposition of this axis 13, as indicated by arrow 21. The follower member18 is thus moving continuously to the right in the figure, but now witha reduced speed. The maximum stroke of this arm arrangement depends onthe available angle interval and the length of the arm 14. One notices,however, that the arm 14 will not be able to force the carrier 16 infront of the attachment point 26 to the chain 10 with any simple means.

[0033] In order to get the follower means 18 to move in front of theaxis 13, the angle of the arm 14, referring to the vertical direction,has to be larger than slope β of the guiding structure 20. Furthermore,passing this threshold angle, the mechanical behaviour of the followermeans 18 may not be stable, i.e. the follower means 18 may then chooseeither to move in front of the axis 13 or behind. Constructiontolerances may also influence the behaviour, and the arm 14 may simplybe stuck in such situations. The angle interval is therefore normallyrestricted to backward movements, i.e. less than 90 degrees.

[0034] According to the present invention, in order to minimise thenecessary space around the conveyor, a short arm length is selected. Inorder to achieve a large total stroke anyway, the arm is provided with afollower member arrangement giving possibilities for turning angleintervals of up to close to 180 degrees. The principles of the action ofsuch arm arrangements are illustrated by the embodiments in the FIGS. 4ato 4 d.

[0035] In FIG. 4a, an arm member 14 is pivotably attached to a chain 10by an axis 13. The chain is moved in the direction indicated by arrow12. A carrier means 16 is attached to the lower part of the arm member14 in a pivotable manner (not shown). The arm member 14 of the presentembodiment is provided with a follower member arrangement comprising twofollower members, a front follower member 18-A and a rear followermember 18-B. When none of the follower members 18-A and 18-B are incontact with any supporting surface, the carrier means 16 is hanging ina vertical direction due to gravitational forces. The connection linebetween the axis 13 and the front follower member 18-A then defines anangle α with the vertical direction. In the corresponding manner, theconnection line between the axis 13 and the rear follower member 18-Bdefines an angle γ with the vertical direction. As indicated in FIG. 4a,the angles are defined to be positive if the vertical line passes inbetween the two follower members 18-A and 18-B.

[0036] In FIG. 4a, a situation is illustrated, where a guiding structure20 just comes into contact with the rear follower member 18-B. Thedistance between the guiding structure 20 and the path of the chain 10decreases in the motion direction 12. The arm 14 behaves substantiallyas prior art arms and the rear follower member 18-B forces the arm toturn backwards, with respect to the axis 13 and the driving direction 12as indicated by the arrow 21. The speed of the carrier means 16 isreduced as compared with the speed of the axis 13.

[0037] In FIG. 4b, the rear follower member 18-B has been used as inFIG. 4a to turn the arm 14 backwards. The guiding structure 20 is,however, in the illustrated portion now pointing somewhat downwards,i.e. the distance between the guiding structure 20 and the path of thechain 10 increases in the motion direction 12. The arm 14 is therebygradually allowed to swing forwards, with respect to the axis 13 and thedriving direction 12 as indicated by the arrow 15. The speed of thecarrier means 16 is now higher than the speed of the axis 13.

[0038] In FIG. 4c, a situation is illustrated, where a guiding structure20 instead comes into contact with the front follower member 18-A. Thedistance between the guiding structure 20 and the path of the chain 10decreases in the motion direction 12. If the angle α of the frontfollower member 18-A is larger than the slope β of the guiding structure20, the front follower member 18-A will be pushed in front of the axis12. The arm 14 thereby turns forwards, with respect to the axis 13 andthe driving direction 12 as indicated by the arrow 17. The speed of thecarrier means 16 is during such a motion higher than the speed of theaxis 13. Once the arm starts to turn forwards, the angel α increases,whereby the slope β of the guiding structure 20 also can be increased.However, the angles α and β should never be allowed to be essentiallythe same, since this may introduce mechanical jamming configurations.

[0039] In FIG. 4d, the front follower member 18-A has been used as inFIG. 4b to turn the arm 14 forwards. The guiding structure 20 is,however, in the illustrated portion now pointing somewhat downwards,i.e. the distance between the guiding structure 20 and the path of thechain 10 increases in the motion direction 12. The arm 14 is therebygradually allowed to swing backwards, with respect to the axis 13 andthe driving direction 12 as indicated by the arrow 19. The speed of thecarrier means 16 is now lower than the speed of the axis 13.

[0040] From the FIGS. 4a to 4 d, anyone skilled in the art understandsthat almost any motion behaviour of the arm 14 may be achieved, bycombining the four motion modes. Different speeds of the carrier means16 are available although the chain 10 moves at a constant speed. Alsodifferent inter-distances between two consecutive carrier means 16 arepossible to achieve. Since the available angle range, in which a stablemechanical guiding is provided, is large, a relatively largeinter-distance adjustment is possible to perform with a relatively shortarm member 14 length. In a preferred embodiment, the length of the arm14 is of about the same magnitude as the height of the carrier means 16.Even more preferable, the length of the arm 14 is less than orsubstantially equal to the height of the carrier means 16.

[0041] The arm members according to the present invention can be formedin many ways. At least two follower members are provided at the samerigid arm structure. Furthermore, it is advantageously if a lineconnecting the pivotable attachment point of the conveying means and themiddle of the attachment means of the carrier means goes between thefollower members. In other words, the follower members are preferablypositioned at each side of the connection line. With the definitions ofFIG. 4a, this means that the angles α and γ both are positive. Thisangle has preferably value that is significant larger than zero, inorder to allow for steeper slopes in situations as the one illustratedin FIG. 4c. However, a too large value will reduce the available tiltingangle range.

[0042] In FIGS. 4a-e, the follower members are positioned at the samedistance from the axis 13 and have the same diameter and protrusionlength. The follower members may, however, depending on the actualapplication, also be positioned at different distance from the axis 13.Different distances simplify typically the application of differentsegments of the guiding surface to come into contact with the followermembers. Furthermore, differences in the follower member size along thearm surface, i.e. the diameter have basically the same effect, and alsothe size perpendicular to the arm surface, i.e. the protrusion lengthmay differ.

[0043] It is preferred, if the follower members are provided with freelyrotating wheels, which are to come into contact with the guidingsurface. This reduces the frictional forces against the guiding surfaceconsiderably.

[0044] The shape of the arm member can be varied almost infinitely. InFIGS. 4a-e, a triangular form is illustrated. Different types of crossesor double arm structures may also be used, depending on the intendedapplication.

[0045] Arm arrangements according to the present invention are useful inmany applications. In the following, an irradiation equipment comprisingsuch a conveyor arrangement will be described somewhat more in detail.Some useful and preferred embodiments of the conveyor systems will atthe same time be described. Particle and/or electromagnetic radiation isin many applications used for sterilising purposes or for materialmodifying purposes. Common for such irradiation equipment is that theytypically allow for very small spaces for conveying means, and that theconveyor path is labyrinthed.

[0046] An irradiation equipment 1 is schematically illustrated in apartly exploded view, with certain parts completely removed in order toincrease the visibility. The equipment comprises an upper irradiationhead 30 and a lower irradiation head 32, between which an irradiationsector 34 is situated. The upper irradiation head 30 and its associatedradiation shield 38 are lifted in the illustration in order to revealthe irradiation section more clearly. The irradiation heads arepreferably designed according to the disclosure of the internationalpatent application WO 99/00801, but other designs are also possible.Also designs with irradiation towards the irradiation sector from onlyone side are useful. Also the lower irradiation head 32 is surroundedwith radiation shields 40, 42, 44, and further shields are removed touncover the essential parts of the equipment. Support sections 52support the entire equipment 1.

[0047] A conveyor arrangement 36 is arranged in a labyrinthconfiguration of alternating vertical and horizontal portions. Thelabyrinth configuration is caused by radiation, restrictions. Inoperation, items within the irradiation sector 34 will be irradiated byelectron radiation. The radiation is partly absorbed in the items andsurrounding parts of the equipment, e.g. the conveyor arrangement and apart of this absorbed radiation will give rise to secondary radiation inthe form of particle of electromagnetic radiation. Such secondaryradiation is emitted in arbitrary directions, and a part of it isemitted along the conveyor. By introducing a number of sharp turns onthe conveyor, surrounded by radiation shields, the secondary radiationwill not be able to escape from the irradiation equipment until hittingthe radiation shield a couple of times. In order to reduce the escapingradiation to allowed levels with the present embodiment, four turns onthe conveyor path on each side of the irradiation sector 34 werenecessary. In FIG. 5, the radiation has to go as far as to the exit port46 in order to escape from the equipment 1.

[0048] The conveyor arrangement 36 of this irradiation equipment 1comprises a conveyor channel 48, which encloses the conveyor arrangement36 during the labyrinth portions of the path. The conveyor channel 48 ismade in stainless steel. In and in the vicinity of the irradiationsector 34, the conveyor channel 48 is omitted in order to give theradiation full access to the items to be irradiated. The conveyorarrangement 36 has an entrance port 50 and an exit port 46, at which theconveyor arrangement 36 is interfaces with other conveyor systems orside equipment. The function of such devices are different from case tocase and are of no particular interest for the present invention andwill therefore not be described in detail. The only requirement for suchside equipment is that they should be able to load and unload items tobe irradiated.

[0049] A driving motor (not shown) drives a belt 54, which in turndrives a wheel 56 and therewith connected gear wheel 58 at the frontside and a corresponding gear wheel at the backside (not shown). Eachgear wheel 58 is arranged to drive the conveying means of the conveyorarrangement 36—a pair of chain, which for general visibility is notshown in the figure. The chains are further arranged around non-drivengear wheels 58 (only some are visible in the figure) to define aconveyor path. Each chain is provided with arm members, furtherdescribed below, which are arranged to engage with opposite ends ofcarrier boxes 100, also described in detail below.

[0050] The carrier boxes 100 are provided from the entrance sideequipment or entrance conveyor to the entrance port 50 and containsitems to be irradiated. The arm member grip the carrier boxes 100successively and carry them into the entrance labyrinth 64. The carrierboxes are, according to the previous discussion, conveyed with a certaininter-distance, in order to avoid collisions. When the carrier boxes 100are leaving the entrance labyrinth 64 and enter into the irradiationsector 34, the arm members according to the present invention are guidedto bring the carrier boxes 100 into contact or near contact with eachother. This is described more in detail below. This close relationbetween the carrier boxes 100 is maintained through the entireirradiation sector 34, while the speed is somewhat reduced in comparisonwith the speed of the chain pair. When the carrier boxes 100 areentering into the exit labyrinth 66, the carrier boxes 100 are allowedto recover the original inter-distance in order to handle the bends ofthe labyrinth. The carrier boxes 100 exit through the exit port 46 andan exit side equipment takes care of the carrier boxes 100 and itsirradiated content, whereby the arm members release their grips. The armmembers are returned to the entrance port 50 through a return passage60, which also is used to return emptied carrier boxes 100 to theentrance side.

[0051] In FIG. 6, an illustration of a preferred embodiment of an armmember 70 according to the present invention is illustrated. A main body72 mainly consists of two arms 74, 76 arranged in a “V” configuration.In the edge part of the main body, an axis 78 is provided, which fitswith a rotational bearing into joints of the chain arrangement. The axis78 and the chain provides a pivoting attachment means. The arm member 70is provided with a front follower member 80, comprising a shaft 84 and afreely rotatable wheel 84.

[0052] The arm member 70 is according to the present invention alsoprovided with a rear follower member 86, comprising a shaft (not shown)and a freely rotatable wheel 88. The wheel 84 has in this embodiment alarger radius than the wheel 88, and the shaft 84 is provided at asmaller distance from the axis 78, than the not shown shaft of the rearfollower member 86.

[0053] Close to the free ends of the arms 74 and 76, respectively,carrier-supporting members 90 and 94, respectively, are provided. Inthis embodiment, each carrier supporting member 90, 94, comprises afreely rotatable grooved wheel 92, 96. The carrier supporting membersare protruded in the opposite direction to the follower members 80, 86.

[0054]FIG. 7a illustrates a carrier box 100, comprising a bottom 102,two long side walls 104, 106 and two short side walls 108, 110. On eachof the short side walls 108, 110, a catching plate 112 is provided (onlyone is shown). The catching plate 112 has two protruding portions 114,116, which are provided with a groove 118 open towards the bottom 102.The grooves are formed for interaction with the carrier supportingmembers 90, 94 of the arm member 70 (FIG. 6). When the carriersupporting members 90, 94 are brought from below up into the grooves118, they will engage with the catching plates 112 and lift the carrierbox 100.

[0055]FIG. 7b illustrates a carrier box 100, lifted by two arm members70. The arm members 70 are in turn pivotably attached to a chain at eachside of the carrier box 100, indicated by a broken line.

[0056] The engagement of the two carrier supporting members 90, 94 andthe grooves 118 gives the conveyor arrangement double attachment pointsbetween the carrier box 100 and the arm member 70. These doubleattachment points stabilise the box during the parts of the conveyorpath where the carrier box 70 hangs freely in the arm members 100. Thecarrier box 100 will not be able to turn around due to any asymmetricloading of the carrier box 100. When the arms 74, 76 are forced to tiltin the vicinity of the irradiation section 34 (FIG. 5), one of thecarrier supporting members 90, 94 is forced out from the correspondinggroove 118 and only one attachment point remains. During this section ofthe conveyor path—the irradiation sector 34, an additional support forthe carrier box 100 has to be provided, in this embodiment a series ofrollers. However, when the arm members 70 are allowed to tilt backagain, the released carrier-supporting member 90, 94 regains its gripinto the groove.

[0057] The irradiation sector 34 is the most important portion of theconveyor path. Here, the carrier boxes 100 are to be packed side-by-sideand brought in a smooth manner through the radiation in order for theitems carried in the boxes to be irradiated. This controlled motion isaccomplished by providing a guiding surface for the double followermembers 80, 86. Only one follower member is in contact with the guidingsurface at the time, while the other is inactive. In FIG. 8, thearrangement for the guiding is illustrated. A pair of guiding surfaces120, 122 is provided at the sides of the irradiation sector 34. Eachguiding surface 120, 122 comprises four segments.

[0058] A first segment 124 is arranged in order to be in contact withthe front follower member and force the arm member in the forwarddirection. The inter-distance between consecutive carrier boxes isreduced until they are conveyed side by side. During this first segment,the distance between the guiding surface and the chain path is reduced.At the same time, the rear carrier-supporting member 94 is forced outfrom the corresponding groove in the carrier box 100.

[0059] A second segment 126 is arranged in order to gradually let thearm members return to their original direction by gradually increasingthe distance between the guiding surface 120, 122 and the chain path.This gradual increase is arranged so that the arrangement of the carrierboxes side by side is maintained. The mean speed of the carrier boxes isin the meantime somewhat lower than the speed of the chain. The rearcarrier-supporting member 94 gradually retains its engagement with tiecorresponding groove in the carrier box 100.

[0060] When the arm members are back in the original angle position, thethird segment 128 begins. In this segment, the front follower member 80looses its contact with the guiding surface 120, 122, and instead therear follower member comes into contact with the guiding surface 120,122. During this third segment, the distance between the guiding surfaceand the chain path is reduced gradually, which forces the arm member toswing backwards. This gradual reduced distance is arranged so that thearrangement of the carrier boxes side by side is maintained. The meanspeed of the carrier boxes is in the meantime still somewhat lower thanthe speed of the chain. The front carrier-supporting member 94 nowgradually looses its engagement with the corresponding groove in thecarrier box 100.

[0061] A fourth segment 130 is finally arranged in order to restore theoriginal relative positions of the carrier boxes. During this fourthsegment, the distance between the guiding surface and the chain path isincreased, which allows the arm to swing forwards, until the carrierboxes hangs freely. The front carrier-supporting member 94 retains itsengagement with the corresponding groove in the carrier box 100. Theinter-distance between consecutive carrier boxes is increased until theoriginal inter-distance is reached. The carrier boxes are ready to enterinto the labyrinth again.

[0062] Since the tilting of the arm members also influences the verticaldistance between the chain path and the carrier boxes, the chain pathhas to be adjusted, in order to keep the path of the carrier boxeslinear. The chains are therefore guided through a guiding groove 134 ina guiding block 132 at each side of the irradiation section 34. Theguiding groove 134 forces the chains to follow a bent path within theirradiation section 34, which allows for a linear carrier box motion.The guiding surfaces 120, 122 are of course adapted to this bent chainpath. Therefore, the guiding surfaces are somewhat bent upwards, despitethe fact that the distance to the chain path is largest in the centrepart.

[0063] In FIG. 9, a schematic illustration shows how the entire movementof the arm members is performed. Here the forward tilting in the firstsegment 124 is seen, followed by the straighten-up in the second segment126. In the third segment 128, the arm member 70 is tilted in theopposite way, and finally in the fourth segment 130 the arm member 70 isagain allowed to be placed vertically.

[0064] In FIG. 10, a flow diagram of a method according to the presentinvention is shown. The process starts in step 200. In step 202, acarrier means is connected to a conveying means by one or several armmembers. In step 204, the carrier means is conveyed by moving theconveying means along a closed loop path. During this motion, a firstengaging means is guided along a first part of a predetermined path,according to step 206. Furthermore, a second engaging means is guidedalong a second part of the predetermined path, according to step 208.The process ends in step 210. This process is in reality a continuousprocess, which is indicated by the broken arrow from the stop step 210to the start step 200. The steps 204 and 206 are performedsimultaneously, and the steps 204 and 208 are also performedsimultaneously. However, steps 204 and 206 are preferably not performedat the same time.

[0065] It will be understood by those skilled in the art that variousmodifications and changes may be made to the present invention withoutdeparture from the scope thereof, which is defined by the appendedclaims. The conveyor means may comprise chains, wires, belts, bands orany other flexible means that can be driven around a closed loop. Thecarrier means does not have to be designed as a rigid unit. If the itemsto be transported are suitable, the carrier means may be formed simplyas attachment means directly fixed to the items to be transported. Anytype of means for carrying may be used, depending on the actualapplication.

1. Conveyor arrangement comprising: conveying means (10) defining aclosed loop path, said path having portions with substantially differingslopes with reference to the horizontal plane; driving means (54, 56)arranged to drive the conveying means around the closed loop path; aplurality of arm means (14; 70), pivotably connected to the conveyingmeans (10) around a substantially horizontal axis (13; 78) for travelingalong the closed loop path; guiding means (20; 124), arranged in thevicinity of the closed loop path, whereby a follower member arrangement(18-A, 18-B; 80, 86) of the arm means (14; 70) being forced in contactwith the guiding means (20; 124) during at least a part of the travelalong the closed loop path; and carrier means (16; 100), being pivotablyconnectable to said arm means (14; 70), characterised in that thefollower member arrangement comprises a first engaging means (18-A; 80)and a second engaging means (18-B; 86), whereby the first engaging means(18-A; 80) is forced in contact with a first section (120, 122, 126) ofthe guiding means (124) during a first part of the travel along theclosed loop path, and the second engaging means (18-B; 86) is forced incontact with a second section (128, 130) of the guiding means (124)during a second part of the travel along the closed loop path. 2.Conveyor arrangement according to claim 1, characterised in that thefirst and second part of the travel have no common parts, whereby onlyat the most one of the engaging means (18-A, 80, 18-B, 86) is forced incontact with the guiding means (20; 124) at a time.
 3. Conveyorarrangement according to claim 1 or 2, characterised in that the first(18-A, 80) and second (18-B, 86) engaging means are provided at oppositesides of a connection line between the attachment axis (13; 78) of thearm means (14; 70) and the centre of the connection (112) of the carriermeans (16; 100).
 4. Conveyor arrangement according to claim 1, 2 or 3,characterised in that the first (18-A, 80) and second (18-B, 86)engaging means are protrusions provided with rollers (82, 88). 5.Conveyor arrangement according to claim 4, characterised in that theprotruding distances of the protrusions at one and the same arm means(14; 70) are different.
 6. Conveyor arrangement according to any of theclaims 1 to 5, characterised in that the first (18-A, 80) and second(18-B, 86) engaging means are forced against the guiding means (20; 124)by gravitational forces.
 7. Conveyor arrangement according to any of theclaims 1 to 6, characterised in that the engaging means (18-A, 80, 18-B,86) are arranged at different distances from the axis (13; 78) betweenthe conveying means (10) and the arm means (14; 70).
 8. Conveyorarrangement according to any of the claims 1 to 7, characterised in thatthe arm means (70) comprises at least two carrier supporting members(90, 94), and the carrier mean (100) have catching means (118) forreleasable engagement with each one of the carrier supporting members(90, 94).
 9. Conveyor arrangement according to claim 8, characterised inthat the only one carrier supporting member is in engagement with thecatching means (118) during the first and second part of the travelalong the closed loop path.
 10. Conveyor arrangement according to any ofthe claims 1 to 9, characterised in that the conveying means (10)comprises a chain.
 11. Conveyor arrangement according to any of theclaims 1 to 10, characterised in that the arm means (14; 70) areconnected to the conveying means (10) at regular distances.
 12. Conveyorarrangement according to any of the claims 1 to 11, characterised inthat the guiding means (20; 124) is present in the vicinity of theclosed loop path only in a limited region, whereby the arm means (14;70) are freely pivotable under the influence of gravitational forcesoutside said limited region.
 13. Conveyor arrangement according to anyof the claims 1 to 12, characterised in that the distance between theaxis (13; 78) and the connection (90, 94, 118) between the arm means(14; 70) and the carrier means (16; 100) is of the same magnitude as theheight of the carrier means (16; 100).
 14. Conveyor arrangementaccording to any of the claims 1 to 13, characterised in that theguiding means (20; 124) having a section (120) where the front engagingmeans (18-A; 80), as defined by the arm travel direction (12), is forcedin contact, said section being arranged with a decreasing distancebetween the closed loop path and the section surface in said forwarddirection, whereby a carrier (16; 100) is forced forwards with respectof the axis (13; 78) between the driving means (10) and the arm means(14; 70).
 15. Conveyor arrangement according to any of the claims 1 to13, characterised in that the guiding means (20; 124) having a section(126) where the front engaging means (18-A; 80), as defined by the armtravel direction (12), is forced in contact, said section being arrangedwith an increasing distance between the closed loop path and the sectionsurface in said forward direction, whereby a carrier (16; 100) ispermitted to move backwards with respect of the axis (13; 78) betweenthe driving means (10) and the arm means (14; 70).
 16. Conveyorarrangement according to any of the claims 1 to 13, characterised inthat the guiding means (20; 124) having a section (128) where the rearengaging means (18-B; 86), as defined by the arm travel direction (12),is forced in contact, said section being arranged with a decreasingdistance between the closed loop path and the section surf ace in theforward direction, whereby a carrier (16; 100) is forced backwards withrespect of the axis (13; 78) between the driving means (10) and the armmeans (14; 70).
 17. Conveyor arrangement according to any of the clans 1to 13, characterised in that the guiding means (20; 124) having asection (130) where the rear engaging means (18-B; 86), as defined bythe arm travel direction (12), is forced in contact, said section beingarranged with an increasing distance between the closed loop path andthe section surface in the forward direction, whereby a carrier (16;100) is permitted to move forwards with respect of the axis (13; 78)between the driving means (10) and the arm means (14; 70).
 18. Conveyingmethod, comprising the steps of: connecting a carrier means (16; 100) toa conveyor means (10) by an arm member (14; 70); and conveying aconveying means (10) along a closed loop path; guiding a follower memberarrangement (18-A, 18-B; 80, 86) of the arm member (14; 70) along apredetermined path substantially along at least a part of the closedloop path, for adjusting the position of the carrier means (16; 100),characterised in that said guiding step in turn comprises the steps of:guiding a first engaging means (18-A; 80) of the follower memberarrangement along a first part of the predetermined path; and guiding asecond engaging means (18-B; 86) of the follower member arrangementalong a second part of the predetermined path.
 19. Conveying methodaccording to claim 18, characterised in that the first and second partsof the predetermined path have no common parts, whereby only at the mostone of the engaging means is guided at a time.
 20. Conveying methodaccording to claim 18 or 19, characterised in that the guiding isperformed by means of gravitational forces.
 21. Conveying methodaccording to claim 18, 19 or 20, characterised in that the guiding isperformed during a limited region of the closed loop path.
 22. Conveyingmethod according to any of the claims 18 to 21, characterised in thatsaid guiding step comprises the step of guiding the front engaging means(18-A, 80), as defined by the arm travel direction (12), in front of theconnection point between the arm member (14; 70) and the conveying means(10).
 23. Conveying method according to any of the claims 18 to 22,characterised in that said guiding step comprises the step of guidingthe rear engaging means (18-B; 86), as defined by the arm traveldirection (12), behind the connection point between the aim member (14;70) and the conveying means (10).
 24. Conveying method according toclaim 22 or 23, characterised in that said guiding step comprises thestep of guiding the front engaging means (18-A; 80) or the rear engagingmeans (18-B; 86), forwards in relation to the connection point betweenthe arm member (14; 70) and the conveying means (10), thereby giving thecarrier means (16; 100) a speed which exceeds the speed of the conveyingmeans (10).
 25. Conveying method according to claim 22 or 23,characterised in that said guiding step comprises the step of guidingthe front engaging means (18-A; 80) or the rear engaging means (18-B;86), backwards in relation to the connection point between the armmember (14; 70) and the conveying means (10), thereby giving the carriermeans (16; 100) a speed which is less than the speed of the conveyingmeans (10).
 26. Irradiation device, having an irradiation source (30,32), emitting radiation in an irradiation sector (34) and a conveyorarrangement for transporting items through the irradiation sector (34),characterised in that said conveyor arrangement comprises: conveyingmeans (10) defining a closed loop path, said path having substantiallyhorizontal portions and substantially vertical portions; driving motorarranged to drive the conveying means (10) around the closed loop path;a plurality of arm means (70), pivotably connected to the conveyingmeans (10) around a substantially horizontal axis (78) for travellingalong the closed loop path, said arm means (70) having a follower memberarrangement (80, 86), which comprises a first engaging means (80) and asecond engaging means (86); guiding means (124), arranged in thevicinity of the closed loop path, whereby the first engaging means (80)is forced in contact with a first section (120, 122, 126) of the guidingmeans (124) during a first part of the travel along the closed looppath, and the second engaging means (86) is forced in contact with asecond section (128, 130) of the guiding means (124) during a secondpart of the travel along the closed loop path; and carrier means (100),being pivotably connectable to said arm means (70).
 27. Irradiationdevice according to claim 26, characterised in that at least a segmentof said first and second parts of the travel along the closed loop pathare comprised within said irradiation sector (34).
 28. Irradiationdevice according to claim 27, characterised by a first segment (126) ofsaid guiding means (124), where the front engaging means (80), asdefined by the arm travel direction, is forced in contact, said firstsegment (126) being arranged with an increasing distance between theclosed loop path and the first segment surface in said forwarddirection, whereby a carrier (100) is allowed to move backwards withrespect of the connection point between the driving means (10) and thearm means (70); a second segment (128) of said guiding means (124),where the rear engaging means (86), as defined by the arm traveldirection, is forced in contact, said second segment (128) beingarranged with a decreasing distance between the closed loop path and thesecond segment surface in said forward direction, whereby a carrier(100) is forced to move backwards with respect of the connection pointbetween the driving means (10) and the arm means (70); said first andsecond segments (126, 128) are extended along the closed loop throughoutthe entire irradiation sector (34).
 29. Irradiation device according toclaim 28, characterised in that said first and second segments (126,128) have shapes, which position carriers (100) within the irradiationsector (34) substantially in close connection to each other. 30.Irradiation device according to claim 28 or 29, characterised in thatsaid first and second segments (126, 128) have shapes giving a carrier(100) a speed through the entire irradiation sector (34), which is apredetermined fraction of the speed of the conveyor means (10).